Isotactic polymers and method of producing same



United States Patent 3,269,995 ISGTACTIC PULYMERS AND METHOD OFPRGDUCHNG SAME Kiyoshi Fujii, Kurasiiilri, Japan, assignor to KurashikiRayon Co., Ltd., Kurashilri-shi, Japan, a corporation of Japan N0Drawing. Continuation of application Ser. No. 118,498, June 21, 1961.This application July 8, 1964, Ser. No. 381,249 Claims priority,application Japan, May 27, 1961, 36/118,655 14 Claims. (Cl. 260-891)This application is a continuation of my patent application Serial No.118,498, filed June 21, 1961, now abancloned.

This invention relates to isotactic polyvinyl esters and isotacticpolyvinyl alcohols derived therefrom, and to processes for making them.

It is an object of this invention to provide polyvinyl esters andpolyvinyl alcohols which are characterized by being isotactic.

It is a further object of the invention to provide processes forproducing isotactic polymers of the character indicated.

In accordance with the invention, isotactic polyvinyl esters areproduced by acylation of a polyvinyl ether, using an organic acidanhydride and a Lewis acid. The resulting isotactic polyvinyl ester isthen readily converted to an isotactic polyvinyl alcohol by conventionalhydrolysis techniques. Polyvinyl alcohol is a polymer containinghydroxyl groups and corresponding to the formula:

wherein n is an integer which can vary within wide limits, as iswell-known in the art. Polyvinyl alcohol can be produced from thecorresponding polyvinyl ester, e.g. polyvinyl acetate, by alkaline oracid saponification or re-esteri-fication, i.e. alcoholysis, inaccordance with the following equation:

CH CH- H or i l OCOR n ROH -OHzCI-I nHOCOR or nROCOR a.

The foregoing reactions are referred to generally by the termsaponification in accordance with conventional practice.

With respect to known saponifica-tion processes and techniques,reference is suitably made, for example, to Bristol U.S. Patent2,700,035, Waugh et al. U.S. Patent 2,642,419 and Germain US. Patent2,643,994.

It has been found that polymers of a vinyl ether can be converted,without destroying their tacticity, to polyvinyl esters by acylationusing an anhydride of an organic acid, e.g. acetic anhydride, propylanhydride, butyric anhydride, and the like, and a Lewis acid such asstannic chloride or zinc chloride.

Cleavage of ethers by means of acid anhydrides in the presence of Lewisacids results in the formation of the corresponding esters, depending onthe anhydride used, and, for example, if a mixed ether is cleaved,benzyl and tertiary-butyl groups are split preferentially to secondaryand primary groups. In accordance with this invention, this reaction isapplied to polymers of vinyl ethers having a cleavable ether linkage inthe side chain. Vinyl ethers suitably employed are vinyl tert-butylether and vinyl benzyl ether. The reaction is complete and the retentionof the isotactic structure during the reaction is confirmed by X-rayexamination of the product. Isotactic polyvinyl 3,269,995 PatentedAugust 30, 1966 alcohols, which are produced in accordance with themethods of the present invention, by conventional saponification orhydrolysis of the polyvinyl ester produced, give a fiber diagram whichresembles that of ordinary polyvinyl alcohol and the repeat distancealong the fiber axis is 2.5 A. But when these polyvinyl alcohols areformylated, they give fiber patterns entirely different from those ofordinary syndiotactic polyvinyl formate, thus proving their isotacticstructure. The identity period is 6.55 A., which shows the existence ofthree helicoidal units. lsotactic polyvinyl alcohols are characterizedby their strong resistance to boiling water.

Many attempts to convert polyvinyl ethers to polyvinyl alcohols haveheretofore been made, but in all cases replacement is not complete, andsometimes the finished polymer contains foreign groups because of thehigher reactivity of the hydroxyl groups.

An important advantage of the present invention is the elimination ofside reactions. As will be seen from the reaction mechanism,

the introduction of foreign groups other than ester groups does notoccur and the results of actual reaction confirm this to be so.

Another advantage of the present invention is that the reaction proceedseffectively in a homogeneous system. Sometimes the polymer is salted outas a gel on addition of the catalyst, but by repeating the reaction,full completion of the replacement can be achieved.

The invention will be further understood trom the following specificexamples of practical application. However, it will be understood thatthese examples are for purposes of illustration only and are not to beconstrued as limiting the scope of the present invention in any manner.

Example 1 To 10 ml. of vinyl tertbutyl ether, 40 ml. of n-hexane wereadded and the mixture was maintained at 78 C. To this mixture were added10 drops of boron trifluoride etherate. After 2 hours, the mixture wasadded to a methanol-water mixture containing caustic alkali to quenchthe catalyst and precipitate the polymer. The polyvinyl tertbutyl etherthus obtained was dissolved in benzene and precipitated with methanol.The polymer was reprecipitated three additional times and was finallydried to constant weight. The yield was 7.7 g. The intrinsic viscosityof the polymer in benzene was about 0.184 (l./gr.) at 30 C.

Two grams of the polymer in 10 ml. of acetic anhydride and 20 ml. ofbenzene were treated with 0.8 gr. of zinc chloride in 5 ml. of aceticanhydride and 10 ml. of benzene at room temperature. Instantly themixture turned dark green and gelified. The mixture was dissolved inbenzene and precipitated with n-hexane. The polymer was repreci-pitatedthree additional times and was then dried to constant weight.

The dried polymer was dissolved in 20 ml. of benzene and 10 ml. ofacetic anhydride. To this solution, 0.8 gr. of stannic chloride in 5 ml.of benzene and 5 ml. of acetic anhydride were added at room temperature.After 5 minutes, the reaction mixture was added to n-hexane and theprecipitated polymer was dissolved in methanol and precipitated withwater. After three reprecipitations, the polymer was dried, and weighed1.4 g.

This polymer was dissolved in 28 ml. of methanol, and to this solution'were added 14 ml. of a 1 N soltuion of caustic soda containing hydrousmethanol, to effect sapon- Iification of the polymer, at 40 C.

The infrared spectrum of the resulting white polymer agreed well withthat of ordinary polyvinyl alcohol, and

the X-ray fiber diagram of the polymer also agreed well with that ofordinary polyvinyl alcohol, the repeat distance along the fiber axisbeing 2.5 A.

This polyvinyl alcohol was then 100% for-mylated in anhydrous formicacid using monochloroacetic acid as a catalyst. Unlike ordinarypolyvinyl formate, the thus-produced formylated polymer was found to beinsoluble in hot acetonitrile and dimethylformamide. This polymer gave asharp X-ray diagram, the identity period being 6.55 A. It was isotacticand exhibited high resistance to boiling water, unlike ordinarypolyvinyl alcohol.

Example 2 The polyvinyl tert-butyl ether used in Example 1 (2 gr.) wasdissolved in 30 ml. of benzene and ml. of acetic anhydride. To thismixture, 2 gr. of stannic chloride in ml. of benzene and 2 ml. of aceticanhydride were added. After 5 minutes, the polymer was recovered as inExample 1.

The finished polymer was substantially tree of color, and 98% of theether groups had been removed and their replacement with acyl groups wasalmost complete. On infrared analysis a small amount of hydroxyl groupswas observed. This polyvinyl alcohol exhibited the characteristicsobserved in the polymer produced in Example 1.

Example 3 There were dissolved 10 ml. of vinyl tert-butyl ether in m1.of toluene and the mixture was kept at 78 C. To this mixture, 0.023 ml.of aluminum diethyl chloride in 10 ml. of toluene was added undernitrogen. After 18 hours reaction at -78 C., the reaction mixture wasadded to methanol. The yield of polymers was 1.1 gr. and the polymerthus obtained was treated as in Example 1, and there was produced anisotactic polyvinyl ester, and an isotactic polyvinyl alcoholcharacterized by high resistance to boiling water.

Example 4 Ten ml. of vinyl benzyl ether were dissolved in 16 ml. ofchloroform and 20 ml. of n-hexane and the mixture was maintained at 60C. To this mixture, 20 drops of boron trifiuoride etherate were added.After 2 hours polymerization, 4.2 gr. of polyvinyl benzyl ether wereobtained. To 2 gr. of this polyvinyl benzyl ether in 20 ml. of tolueneand 10 ml. of acetic anhydride, 1.98 gr. of stannic chloride were addeddropwise at room temperature. Upon the addition of the stannic chloride,the temperature rose and the reaction mixture turned to a dark brownishcolor.

After 5 minutes, the reaction mixture was added to petroleum ether andthe polymer precipitated. The polymer was dissolved in amethanol-acetone mixture and was then precipitated with water. Thepolymer was reprecipitated with water and the polymer was thenreprecipitated three additional times and finally dried to constantweight. The yield was 1.2 gr. Infrared spectrum and elementary analysisshowed that the polymer obtained was polyvinyl acetate and that it wasisotactic. Following the procedure described in Example 1, it wasreadily convertible to an isotactic polyvinyl alcohol.

The conditions and the relative relationships set forth in the examplesare those preferred in carrying out the process of this invention, butit will be understood that other conditions and relationships may beused within the scope of the invention. In general, unless otherwiseindicated, conventional operations and techniques are suitably employedin forming the polymers of this invention.

Thus, the treatment with the organic anhydride and with the Lewis acidis readily carried out at room temperature although higher temperaturesmay be employed if desired. The anhydrides are preferably those of loweralkyl carboxylic acids but other organic anhydrides effective to formpolyvinyl esters from polyvinyl ethers which are convertible byconventional saponification are also acetic acid, and the like.

suitably used. The conversion of the polyvinyl ether to the polyvinylester is most advantageously carried out in a solvent for the polyvinylether being treated. An aromatic hydrocarbon such as benzene and tolueneis preferred for this purpose but other solvents which do not react withthe polyvinyl ether and which dissolve it are suitably used.

The crystalline or isotactic polyvinyl ether which is employed is madeby any convenient known means from the corresponding vinyl ethermonomer.

In general, good results are achieved by effecting polymerization of thevinyl ether at low temperatures, e.g. 60 to C. in a hydrocarbon solventwith a Lewis acid or a Lewis acid addition complex or alkyl, such as theboron trifluoride etherate or the aluminum diethyl chloride used in theexamples, preferably in the presence of chloroform.

Lewis acids are, of course, a well-known class of compoundscharacterized by the late Gilbert N. Lewis as electron acceptors.Typical examples of Lewis acids useful in relation to the presentinvention are boron trifluoride, aluminum chloride, aluminum bromide,stannous chloride, stannic chloride, zinc chloride, titaniumtetrachloride, zirconium tet-rafluor-ide, and like inorganic halides,halo-organic acids such as trichloroacetic acid, trifluoro- Thecomplexes of these Lewis acids which are also effective are exemplifiedby the coordination compounds with lower alkyl (1 to 4 carbon atoms)alcohols such as methanol, ethanol, and .butanol, lower 'alkyl etherssuch as diethyl ether, methylethyl ether, dibutyl ether, and propylbutylether, cyclic saturated ethers containing up to six carbon atoms, suchas tetrahydrofuran, and the like.

It will also be understood that various changes and modifications inaddition to those indicated above may be made in the embodiments hereindescribed without departing from the scope of the invention as definedin the appended claims. It is intended, therefore, that all mattercontained in the foregoing description shall be interpreted asillustrative only and not as limitative of the invention.

I claim:

1. Isotactic polyvinyl esters of lower alkyl car boxylic acidsconvertible by saponification to isotactic polyvinyl alcohol where saidisotactic polyvinyl alcohol has a high resistance to boiling water, saidisotactic polyvinyl alcohol being convertible to polyvinyl formate wheresaid polyvinyl tformate is insoluble in hot acetonitrile anddimethylfonmarnide, and where said poly-vinyl formate has an identityperiod of 6.55 A. as shown by its X-ray diagram.

2. Isotactic polyvinyl alcohol having a high resistance to boilingwater, said isotactic polyvinyl alcohol being convertible to polyvinylformate where said polyvinyl formate is insoluble in hot acetonitrileand dimethylformamide, and where said polyvinyl formate has an identityperiod of 6.55 A. as shown \by its X-ray diagram.

3. A process of producing an isotactic polyvinyl ester of a lower alkylcarboxylic acid which comprises reacting a polyvinyl hydrocarbon etherhaving an isotactic structure with an anhydride of a lower alkylmonocarboxylic acid in the presence of a Lewis acid catalyst.

4. A process of producing isotactic polyvinyl acetate which comprisesreacting polyvinyl tert-butyl ether having an isotactic structure withacetic anhydride in the presence of a Lewis acid catalyst.

5. A process of producing isotactic polyvinyl alcohol which comprisespreparing an isotactic polyvinyl ester of a lower alkyl carboxylic acidby reacting a polyvinyl hydrocarbon ether having an isotactic structurewith an anhydride of a lower alkyl monocarboxylic acid in the presenceof a Lewis acid catalyst, and saponifying said prepared isotacticpolyvinyl ester to produce said isotactic polyvinyl alcohol.

6. A process of producing isotactic polyvinyl alcohol which comprisespreparing isotactic polyvinyl acetate by reacting a polyvinylhydrocarbon ether having an isotactic structure with acetic anhydride inthe presence of a Lewis acid catalyst, and saponifying said preparedisotactic polyvinyl acetate to produce said isotactic polyvinyl alcohol.

7. A process of producing isotactic polyvinyl alcohol which comprisespreparing isotactic polyvinyl acetate by reacting polyvinyl tert-ibutylether having an isotactic structure with acetic anhydride in thepresence of a Lewis acid catalyst, and saponifying said preparedisotactic polyvinyl acetate to produce isotactic polyvinyl alcohol.

8. A process of producing an isotactic polyvinyl ester of a lower alkylcanboxylic acid, which comprises reacting a compound selected from thegroup consisting of polyvinyl lower alkyl ethers having an isotacticstructure and polyvinyl aralkyl ethers having an isotactic structurewith an anhydride of a lower alkyl monocarboxylic acid in the presenceof a Lewis acid catalyst.

9. A process of producing isotactic polyvinyl alcohol which comprisespreparing an isotactic polyvinyl ester of a lower alkyl canboxylic acidby reacting a compound selected from the group consisting of polyvinyllower alkyl ethers having an isota-ctic structure and polyvinyl aralkyilethers having an isotactic structure with an anhydride of a lower alkylmonocar-boxylic acid in the presence of a Lewis acid catalyst, .andsaponifying said prepared isotactic polyvinyl ester to produce saidisotactic polyvinyl alcohol.

10. The process of claim 3 wherein the polyvinyl hydrocarbon ether is apolyvinyl C -C ether.

11. The process of claim 3 wherein the polyvinyl hydrocanbon ether is apolyvinyl lower alkyl ether.

12. The process of claim 5 wherein the polyvinyl hydrocanbon ether is apolyvinyl C 0 ether.

13. The process of claim 6 wherein the polyvinyl hydrocanbon ether is apolyvinyl C -C ether.

14. The process Olf claim 5 wherein the polyvinyl hydrocarbon ether is apolyvinyl lower alkyl ether.

JOSEPH L. SCHOFER, Primary Examiner.

J. F. MCNALLY, Assistant Examiner.

1. ISOTACTIC POLYVINYL ESTERS OF LOWER ALKYL CARBOXYLIC ACIDSCONVERTIBLE BY SAPONIFICATION TO ISOTACTIC POLYVINYL ALCOHOL WHERE SAIDISOTACTIC POLYVINYL ALCOHOL HAS A HIGH RESISTANCE TO BOILING WATER, SAIDISOTACTIC POLYVINYL ALCOHOL BEING CONVERTIBLE TO POLYVINYL FORMATE WHERESAID POLYVINYL FORMATE IS INSOLUBLE IN HOT ACETONITRILE ANDDIMETHYLFORMAMIDE, AND WHERE SAID POLYVINYL FORMATE HAS AN IDENTITYPERIOD OF 6.55 A. AS SHOWN BY ITS X-RAY DIAGRAM.
 2. ISOTACTIC POLYVINYLALCOHOL HAVING A HIGH RESISTANCE TO BOILING WATER, SAID ISOTATICPOLYVINYL ALCOHOL BEING CONVERTIBLE TO POLYVINYL FORMATE WHERE SAIDPOLYVINYL FORMATE IS INSOLUBLE IN HOT ACETONITRILE AND DIMETHYLFORMAIDE,AND WHERE SAID POLYVINYL FORMATE HAS A IDENTITY PERIOD OF 6.55 A. ASSHOWN BY ITS X-RAY DIAGRAM.
 3. A PROCESS OF PRODUCING AN IOTACTICPOLYVINYL ESTER OF A LOWER ALKYL CARBOXYLIC ACID WHICH COMPRISESREACTING A POLYVIINYL HYDROCARBON ETHER HAVING AN ISOTACTIC STUCTUREWITH AN ANHYDRIDE OF A LOWER ALKYL NONOCARBOXYLIC ACID IN THE PRESENCEOF A LEWIS ACID CATALYST.